The present invention relates to producing catalytic converters. More particularly, the invention relates to producing catalytic converters, the housing or canister of which is sized according to a specified annulus between the canister and the substrate based upon a measured size of the substrate to be mounted in the canister.
Catalytic converters have been employed in vehicles for more than twenty years and have been manufactured in a number of ways.
One method of manufacturing catalytic converters is to provide a pre-made canister and stuff it with the catalyst substrate and the insulation/support pad. In this method the catalyst substrate is wrapped with an intumescent mat of a selected thickness and weight (various weights are employed for various applications and desired properties). Commonly, the wrapped substrate material will create an assembly having outer dimensions that measure about 8 mm larger than the inside dimensions of the converter shell or canister. The assembly as described is then forced through a reduction cone and into the converter shell. Up to 20,000 lbs of pressure can be required to accomplish the insertion of the assembly into the can. The method is costly.
A commonly preferred method for producing a catalytic converter is known as xe2x80x9cthe tourniquet methodxe2x80x9d. The tourniquet method dispenses with the reducing cone and thus avoids the high insertion pressures on the substrate and mat materials. The method places the substrate and mat assembly into a canister open on one longitudinal edge. The canister is closed around the assembly by straps and compressed to the desired size. The open ends of the canister will, in this position, be overlapping and then are welded together. This method is also expensive and labor intensive. Further, due to this overlap, engineering design consideration must be given to the space alteration inside the canister due to the overlapped edge. The overlapped edge causes a mat density change in the local area of the overlap. This is a further cost addition.
In an effort to avoid the overlap and the need for welding the canister after insertion of the materials, it has been known to insert the assembly, as defined hereinabove, into an oversized metal tube and subsequently to size reduce the tube around the assembly. The tube is reduced to predetermined dimensions to produce a finished catalytic converter. An example of this technology is found in U.S. Pat. No. 5,329,698.
It is an object of the invention to increase control over the density of an intumescent mounting mat within a catalytic converter and to increase control over the amount of pressure placed on the catalytic substrate within the housing canister to provide a long life catalytic converter.
It is another object of the invention to reduce the difficulty of conventional manufacturing processes for the construction of catalytic converters.
Yet still another object of the invention is to reduce manufacturing time and cost.
Advantageously, the method for producing catalytic converters and the catalytic converter produced thereby, achieve the above objects by measuring a catalytic substrate prior to wrapping the same in an intumescent material mat, loading the wrapped catalytic substrate in an oversized canister and size reducing the canister to provide a preselected annulus relative to the measured substrate.